We propose a general investigation of fat metabolism in stressed and non-stressed human newborn infants, focussing particularly upon the essential fatty acids (EFA) and their dietary ratio to vitamin E and with special attention to prostaglandins as the principal biosynthetic product of EFA. By direct gas liquid chromatography measurement of EFA in biological fluids we will assess their role in platelet function during thrombopathic states, the possibly shifting composition of pulmonary surfactant phospholipids during respiratory distress and the occurrence and repair of EFA deficiency during fat-free parenteral alimentation. The possible membrane-destabilizing effects of untoward dietary EFA/vitamin E ratios will be assessed in infants at risk of bronchopulmonary dysplasia. The levels of prostaglandins and their metabolites will be measured by radioimmunoassay in biological fluids. These, along with developmental assessment of the ontogeny of prostaglandin synthetase (kidney) should provide some estimate of prostaglandin turnover during various natural and clinically stressful conditions. These studies should provide means for prompt diagnosis of EFA deficiency and, as well, suggest rational and effective means of treatment and prevention.